In many commercial enterprises, sugar is utilized to a great extent for its sweetening properties. It is used in the sweetening of foods, for the manufacture of syrups and confectionery items, in preserves and jams, as a chemical intermediate for detergents, emulsifying agent and other sucrose derivatives such as plasticizers, resins, glues, etc. The usual derivation of sugar is from cane sugar and sugar beets. It is obtained by crushing and extracting the sugar from the cane with water or extracting the sugar from the sugar beet with water followed by evaporation and purifying with lime, absorbent carbon and/or various liquids. The chief component of this type of sugar is sucrose, while other sugars may contain other polysaccharides such as dextrose and levulose (fructose). Other polysaccharides which possess sweetening properties include glucose, maltose, etc. The various polysaccharides possess varying degrees of sweetness, especially when in pure form and not contaminated by any reversion products.
One source of glucose which possesses a relatively high degree of sweetness and which, in turn, may be converted to fructose, the latter possessing an even greater degree of sweetness, is a starch. As is well known, starch is present in many naturally-occurring plants including corn, potatoes, rice, tapioca, wheat, etc. Heretofore, it has been known to treat starch with an enzyme such as amyloglucosidase to obtain glucose. However, the treatment heretofore provided entailed a relatively long residence time in order to obtain a glucose syrup which contained about 94% glucose. The relatively long residence time which has heretofore been required restricts the throughput of glucose and results in the appearance of reversion products which impart a bitter taste to the glucose, thus negating the sweetening property of the compound as well as requiring further treatment in order to remove the offering product. One such reversion product which imparts a bitter taste comprises isomaltose.
In addition to the reversion products which are formed during the reaction period, some of the polysaccharide remains unconverted. In order to obtain the desired mono- or disaccharide in a relatively pure form, it is necessary to separate these unconverted polysaccharides from the desired reaction product. In addition, if a free enzyme has been used to effect the desired conversion, it must also be separated from the reaction product. As will hereinafter be shown in greater detail, it has now been found that the desired separation process may be effected by separating the reaction mixture comprising monosaccharides, disaccharides, unconverted polysaccharides, and, in some instances, enzyme over an ultra-filtration membrane at a relatively high separation efficiency whereby a purification of the desired sugars is effected.